The Echinoid Directory

Biology and geological history of the Holasteroida

Biology

Today holasteroids live exclusively in the deep-sea, and include the deepest dwelling of all known echinoid species. Little is known about their biology other than they are deposit feeders, apparently collecting surface organic matter via their frontal groove as they move over the sediment surface. Growth and population structure is best known for, Echinosigra, due to the work of Gage (1984).

However, in the Cretaceous many groups are found living in shallow water settings. They resemble spatangoids in many ways, and many were almost certainly infaunal. However, unlike spatangoids, none appear to have developed funnel-building tube-feet. Thus holasteroids could only have lived fully infaunally in moderately porous and permeable sediments. Flat-based forms such as Echinocorysand the stegasterids were probably exclusively epifaunal, while those with more ovate tests such as Infulasterand Cardiaster, may have lived partially buried (see Gale & Smith 1982). Most Cretaceous and many Tertiary holasteroids have enlarged pore-pairs around the mouth identical to those bearing penicillate tube-feet in spatangoids. It seems likely, therefore, that they were selective particle feeders using penicillate tube-feet to pass suitable particles to the mouth.

The first holasteroids appear in the earliest Cretaceous of eastern Europe and North Africa, and are contemporary with the earliest spatangoids. These first species lived in mid-shelf sandy-bottom environments. An initial diversification quickly led to the establishment of a major clade, the Meridosternata (characterized by their meridosternous plastron), by the Hauterivian. However, more primitive protosternous taxa continued to thrive throughout the Cretaceous, with hemipneustids a prominent component of the benthos in deeper water carbonate platform settings of the Late Cretaceous. Hemipneustids survived in continental shelf settings through to the Late Oligocene in Australia and New Zealand, and, in deeper water settings, until the mid Miocene in Europe.

The oldest Meridosternata are species of Holasterfrom the Hauterivian of Europe. With the onset of widespread deep-water conditions over the continental shelves in the Late Cretaceous meridosternate holasteroids thrived and diversified. Many lineages are to be found in the chalks and deep-water limestones of this time. By the Maastrichtian one group, the stegasterids, had moved off the shelf and onto continental slope settings. Stegasterids continued through the Tertiary in exclusively deep-water settings, and one living species, Sternopatagus sibogae de Meijere, survives today in deep water settings.

Stegasterids were the dominant deep-water holasteroids of the Late Cretaceous, but they apparently underwent a major decline at the Cretaceous-Tertiary transition, and it is another group, the Urechinina, that make up the great majority of the living deep-water holasteroids. The origins of the deep-sea urechinine fauna can be traced back to late Cretaceous (Maastrichtian) taxa Galeasterand Basseasterof the chalk seas. However, in the southern hemisphere the urechinine family Corystidae remained a common element of clastic mid-shelf habitats throughout much of the Tertiary. By the Miocene fossil representatives of both pourtalesiids and urechinids are known from deep sea sediments.